Field of the Invention
The invention relates to a simulation device for simulating a peripheral circuit arrangement that can be connected to a control device and a method for simulating a peripheral circuit arrangement that can be connected to a control device.
Description of the Background Art
A circuit for emulating—which is to say for simulating—an electrical load at a terminal of a test circuit is known from the WO 2010 010022 A1, which corresponds to U.S. Pat. No. 8,754,663, and which is incorporated herein by reference. Some elements of FIG. 3 of the aforementioned PCT document are appended to the present document as FIG. 1c for better understanding of the prior art. Said document proposes, in particular, a controllable voltage source as a four-quadrant switching device 17 with an internal voltage source 18. A current flowing from the four-quadrant switching device 17 to the test circuit 3 can be coupled in, more particularly via inductance 14 of a bridge shunt arm.
Depending on the requirements for the dynamics of the circuit for simulation, and depending on the nature of the requirements for avoiding or at least reducing an unwanted superposition of ripple currents on the current in the bridge shunt arm or superposition of an unwanted—possibly high-frequency—AC current on the current in the bridge shunt arm, conventional controllable voltage sources could prove to be inadequate for highly precise simulation applications.
It is a part of general technical knowledge that a multi-phase, in particular three-phase electrical load, for example an electric motor 110 from FIG. 1a, implemented here as a three-phase electric motor, can be connected to a supply circuit, wherein one associated half-bridge circuit for each phase, for instance, can be connected to the relevant phase for current control. FIG. 1a shows an example from the prior art, in which the three phases 101, 102, 103 of an electric motor 110 are supplied by means of a first half-bridge 104, 105, a second half-bridge 106, 107, and a third half-bridge 108, 109, wherein these three half-bridges are composed of field-effect transistors 104, 105, 106, 107, 108, 109, abbreviated as FETs. The drain terminals of the FETs 104, 106, 108 are connected to a common operating voltage 111. The source terminals of the FETs 105, 107, 109 are connected to a common reference voltage GND. The three half-bridges from FIG. 1a are integrated into, for instance, a control device that drives the electric motor 110.
FIG. 1b differs to FIG. 1a in that the electric motor 110 is replaced by an electric motor simulation device 120. It is an approach generally known from the prior art to replace a peripheral circuit arrangement, for example the electric motor 110 from FIG. 1a, with a simulation device, for example an electric motor simulation device 120 from FIG. 1b, for test purposes. A problem frequently encountered with prior art electric motor simulation devices is that they either do not adequately emulate reality, or the prior art electric motor simulation devices cannot be retrofitted with sufficient flexibility to changed electric motors that are to be simulated, or else such retrofits require very extensive hardware changes that are time-consuming.
An appropriate test environment, for example, a simulation device, is frequently used for testing of a control unit or a control device that is to be connected to a peripheral circuit arrangement, for example an electrical load, perhaps an electric motor, in an intended later application.
It is known that an expert active in the technical field mentioned at the outset who wishes to provide a simulation device for simulating a peripheral circuit arrangement that can be connected to a control device oftentimes makes use of a simulation device that includes a computing unit on which executable model code is installed. The model code is based on a mathematical model of the peripheral circuit arrangement. The mathematical model is transformed into model code that can be executed on a computing unit, for instance in a method comprising multiple steps, for example including programming, so-called code generation, and a translation step.
By means of cyclic execution, which is to say cyclic processing, of the model code, predefined output variables are cyclically computed as a function of input variables; these output variables can be used or processed further, for example, to provide voltages and/or currents for simulation purposes.
Testing with the use of a simulation device can in particular offer the advantage that the control unit or the control device can be functionally tested without the need for the control unit or the control device to be placed in its “actual” operating environment. In the above-described context, the control device under test, often referred to as the “control unit” under test, is frequently referred to as the “device under test,” abbreviated as “DUT.” Frequently, the control device or DUT is connected electrically to a suitably configured simulation device in order to test whether the control device responds in the desired manner, which is to say whether the control device responds to specific state variables received through its interfaces with an appropriate output of output variables that are output through its interfaces. The relevant environment of a control device is fully or partially simulated for this purpose.
In generally recognized test scenarios, the environment to be emulated of the control device under test also includes power electronic components, in particular. For example, testing of a control device may make it necessary to provide an emulation, which is to say a simulation, of an electric motor or another electrical load, which also includes, in particular, an inductance simulation. In general, environments of this type can be simulated in software as well as by means of hardware. Frequently, a simulation device, specially designed hardware, and specially adapted simulation software are employed for testing of a control device with power electronic outputs and/or inputs.
Remaining with this example of a simulated electrical load, a distinctive feature of the simulation of an inductive load resides, in particular, in that it is necessary to take into account in the simulation that a change in the magnetic flux density passing through the corresponding actual inductive load, such as can be caused by a switching operation in the control device, results in an induced voltage. The accompanying nonlinear current and voltage curves should be emulated as realistically as possible in the simulation of the electrical load. In other words, the simulation device used in the test phase of the control device should reflect as closely as possible the behavior of an “actual” inductive load that occurs in the later phase of actual practice.
The simulation devices heretofore available, in particular the simulation devices suitable for so-called “hardware-in-the-loop simulation,” abbreviated “HIL simulation,” are lacking in adequate scalability and adaptability, which is to say that the scaling and adapting of previous simulation devices, for the purpose of, e.g., adaptation of the simulation device to different inductive loads to be simulated, requires extensive hardware changes in many cases. Frequently, it has only been possible heretofore to solve the problems resulting from the described inadequate scalability and inadequate adaptability through rebuilding or retrofitting work on the simulation device, especially when the electrotechnical parameters of the inductive loads to be successively simulated differ greatly from one another.
There is a need in the industry and in research and development, especially in product development and quality assurance, for an improved simulation device for simulating a peripheral circuit arrangement, for example for simulating an inductive load.
The simulation of the dynamic behavior of the inductive load by means of model code is often subject to requirements such that the model variables that belong to the model code and are to be computed cyclically must, for example, be computable in execution times in the range of a few milliseconds or even only a few microseconds. In this context, an execution time means the period of time that a computing unit requires in order to process a simulation model code once. In other words, the model code is cyclically executed during a simulation, wherein preferably each processing of the model code takes place within a predefined execution time, and the processing of the model code is essentially repeated for as long as the simulation runs. A model-based simulation such as takes place on the said simulation device presupposes a cyclic—which is to say a repeatedly executable—processing of the model code on the computing unit of the simulation device. Generally speaking, a use of computer-assisted simulation models and a use of associated executable model codes is known, with which the aforementioned execution times for cyclic model code processing can be ensured, namely simulation models, for example, that can be created by means of a numerical development and simulation environment. One example of a development and simulation environment including a graphical programming environment is the software product SIMULINK from the firm The MathWorks. One example of the generation of executable model code, for example by means of the software product SIMULINK, is mentioned in the U.S. Pat. No. 9,020,798 B2, which is incorporated herein by reference.
However, in practice it frequently is not sufficient to merely provide the model variables for describing the dynamically changing state of the inductive load within the predefined execution time by means of the model code; rather, it may be necessary, for example, to carry out the simulation of the peripheral circuit arrangement, for example the simulation of the inductive load, in such a manner that particularly voltages and/or currents are provided at the electrical connection points between the simulation device and the control device(s) that have a high degree of agreement with the dynamically changing voltages and/or currents in an “actual”, which is to say not simulated, peripheral circuit arrangement. The non-simulated peripheral circuit arrangement includes an inductive load, for example.
In other words, it is a requirement to provide the user of the simulation device with a device that is equipped to provide, at the designated electrical terminals of the simulation device, appropriate currents and/or voltages for the control device that in each case exhibit only predefined maximum permissible deviations from the corresponding currents and/or voltages of a later application of the control device.